Telemetric apparatus



March 16, 1954 CARY 2,672,600

TELEMETRIC APPARATUS Filed D80. 13, 1951 flame/Is ('ar INVE rm 55E. gm

Patented Mar. 16, 1954 TELEMETRIC APPARATUS Francis H. Cary, Warwick, It. 1., assignor to B-I-F Industries, Inc., a corporation of Rhode Island Application December 13, 1951, Serial No. 261,501

1 Claims. 1

This invention relates to telemeterin and more especially to the obtaining of desirable signal accuracy throughout the entire range of variation of the magnitudes under measurement. The invention is particularly concerned with telemetering systems of the impulse-duration type wherein there is customarily employed a transmitter having a cam rotatable continuously at substantially constant speed and co-operating with contact means for sending in each of successive cycles of rotation of the cam an electrical impulse of a duration corresponding to a variable magnitude. such as rate of flow, temperature, or pressure.

A limitation of prior apparatus of this type is that accuracy of signal length is diflicult to obtain at low rates where the curvature of the cam approaches the arc of a circle and the angle between the cam edge and the rate arm therefore approaches zero. This is especially true in the telemetric transmitters used in connection with the measurement of flow where the cam is shaped so as to produce a signal proportional to the squareroot of the rate arm displacement.

To produce accurate signals in the low, as well as the higher, range of rates, the present invention provides two transmitters, one of which is of conventional type and the other of which has a specially designed cam which spreads out the low rate range so that accurate signaling in this range is effected.

The two transmitters are connected in parallel to one receiver; and transmitter-selecting means are provided whereby the low rate transmitter is efiective for operating the receiver at low rates :r

only, and the high rate transmitter at high rates only. The rate at any time determines which transmitter is efiective. A further, more speciflc, feature of the invention comprises means governed by the receiver for switching the latter from one to the other of the transmitters, in response to the rate indicated at the receiver.

Other features and advantages of the invention will be hereinafter described and claimed.

In the accompanying drawings there is shown a telemetric system arranged in accordance with my invention and illustrating the features thereof.

In the drawing, It indicates a Venturi tube or other differential pressure producer to which a high differential manometer I2 is connected by pressure pipes l4 and It. A low diflerential manometer I8 is connected in parallel with maangrzneter l2 by means of pressure pi es 2|! an The manometers l2 and IB contain mercury or other suitable liquid which, in well-known manner, is displaced from one well of the manometer to the other well in response to changes in the differential pressure created in the Venturi tube.

In the manometer l2, there is a float 23 resting on the mercury surface. Motion of the float is transmitted to the shaft 24 by means such as a rack 25 and gear segment 26.

Attached to shaft 24 is a rate arm 21 of telemetric transmitter 28. Cooperating with rate arm 2! is a cam 29 continuously rotated by synchronous electric motor 30.

It will be seen that the rate arm 21 will assume a position relative to the center of cam 29 dependent upon the displacement of the float in manometer i2. One wire 3| of a telemetric circuit is connected to arm 21 by means of a brush 33, and another wire 32 of the telemetric circuit is connected to the shaft of cam 29 by means of wire 34 and brush 35.

It will be seen that the circuit through wires 3! and 32 will be completed in the transmitter 28 during that part of each revolution of cam 29 in which the rate arm 21 rides on the cam 29. The cam 29 is so shaped that the duration of the telemetric signal in each cycle is proportional to the position of rate arm 21 relative to the center of cam 29, and therefore to the position of float 23, and therefore to the rate of flow through the Venturi tube Ill.

The manometer l8 contains a float 35, a rack 3'! and a gear segment 38 connected to shaft 39 to position rate arm 40 of telemetric transmitter M in the same manner as described for transmitter 28.

Manometer I8 is of well-known type in which full float travel occurs upon relatively low differential pressure from Venturi tube l0, and manometer i2 is of well-known type in which full float travel occurs upon relatively high difierential pressure from Venturi tube it]. As a result of this combination the rate arm 40 of telemetric transmitter 4| moves over its full range during the low differential range, whereas rate arm 21 of telemetric transmitter 28 moves over its full range during the high differential range.

Cam 42 of transmitter 4| is continuously rotated by synchronous motor 43 and cooperates with rate arm 40 to complete a telemetric circuit from wire 32 to Wire 44 by means of wire 45 and brush 45, rate arm 40, cam 42, and brush 41.

The cam 42 is so shaped'that the duration of the telemetric signal in each cycle is proportional to the position of rate arm Ill relative to the center of cam 42, and therefore to the position of float 36. Thus, the duration of each of said signals is proportional to the rate of flow through Venturi tube Ill within the range of the relatively low rates of flow corresponding to the travel of said float. Said cam is so shaped that for each increment of change of float position within said range, a-snbstantiai cmnge of signal'duration is. effected through the engagement of said cam and the rate arm 40.

When the flow rates in Venturi tube Ill exceed the low range, the manometric liquid inmanom eter I8 merely is displaced downward out of the float chamber without causing fnrttiermovementi of the float. For this purpcseedownward move ment of the float may be limited by engagement of the float with inwardly convergingallace the, manometer chamber, or with any other suitable stop positioned below said float.

The telemetric receivengenerally indicated by the-numerallwiccmprises a crutch unit 49 of Well-.krmwmdesign,.havingv a; member 50 which mo esrin; each in cycle during" the time that the telemctric. signalzis on; and a: member it which moves in each cycle-during the'otlmethat the telemetricsignalis off; Theindieatingpointerfl is positionednialtermtely by. the clutch members andrfi I by-suitahlae linkagesctorindicate the rate of flow. An example of .aasuita'ble'type of; receiver which beemnloyed is illustrated in the Huxford'Patent No; 2,145,026, issued January 24, 1939.

Theipointer 52':is.z.pnovided with an arm 53'on which is mounted a tilting; switch 5! of wellknown typein which aacircnitis made or broken by themovement-tot a; globule of imercury.

When the pointer 52 ispositioned within the range'ohlom'flo wV-rates, the switch 54 is closed, completing apcircuittthrough the reiay'coil 54 by way or wire; connected'tooneterminal of a source: osiielectromotive force, switch 54; coil 54, and wire 63 connected to theioppositeterminal ofssaid source The armaturelifi ofsaid coil 55 is thlereby caused to: engage aicontact 51, establishing a connection. from wire 60" (connected to one terminal of source." of electromotive force) through coil 59; wire 58, and'contact 51 to the previously. mentioned when 441 which extends to the came 421 of the" low-rater transmitter 41. Then, whenever-sure; rate arm'dfli engages said cam 42; the wire Miand coil :5! will be connected to the wire 32 (which in turn is connected tothe opposite terminal oi the'source of electromotive force to which wire 60- is connected) whereupon saidvcoiligr is energized and-its armature 6! is engagediwith aicontact 621 A circuit is thus completed from wire 63 through armature 61, contact, wire: 64; clutch member: 50, wire 65 andibackzto wire 66, whereby said clutch unit is energized;

When theoteiemetriczcircuitithrough wires 44 and'32 is brokenvin'transmitterrfl by the disengagement'of arm 40-Hour 'camr42 during the rotatiorraof said cam; the'coil "59 is deenergized and its armature B l returns into engagement with .a contact: 61. Thereby the: circuit through tclutch 1 unit 50 is s'deenergized randcascircnit is completed from wire 68 throughisaid armature, contact 61, wire 88; clutch 11131151", wire -65; and back to wire 55. Clutch uni-t5! isthus'energized until the cam 42 again engages the ratearmallll, assuming the switch 54% remain closed When theindicatedratecof flow: rises above the: aiorementionedi lower: range; 14.6.}. when: the ppinten-Bkarrivessin the-appsitinmcorrespondingv toithecmaximum ralueaeceived-zirommansmittert 4|, the arm 53 will be positioned so that the switch 54 will open the circuit to coil 55, in which case the armature 56 will move to contact 69, thereby completing a connection from wire 3| through contact 69, armature 56, and wire 58, to coil 58. Under these conditions, it will be apparent that the transmitter 28 will operate the relay coilts anchtheclihtch members 58 and 53 in response to signals -from ratearm 2Tandcam 29, so that said pointer 52 Will indicate values in the higher range for which transmitter 28 is provided If 'the receiver 48 must be located at a considerable distance-ifromrthe transmitters 28 and 4|, it may be undesirabiei to have three wires in the telemetric transmission line. The number of wiresrcanibehreducediby locating the receiver 48 near the transmitters 2B and M and providing in the reeeiver 48 an extra armature l0 and contact II operated by the coil 58. Wires 12 and 13 connectedzirespectively to thearmature 'Hl-andthe contact; I I then: comqariseaa: two-wire:;telemetric. circuitior: operation ofra conventional receiver located remotely.

While a the eforegoingzdcscription has. been :cona fined to" the: telemetering: of flow rates which inherentlyinvolvea squareeroot relation between rate of: flowandsdifierential pressure in which.

the features of'the dual transmitters areparticm larlyo advantageous; it will be understood that'the prineip-ler of'my invention may be applied to the transmission of: linear. or other functions tor obtain greater: accuracy in the-low rate range.-

The terms and expressions which I have em-v ployed are used asmerms-"of description and not of limitation; and Ihave no;intentiorr, in the use of such terms and expressions; of, excluding any equivalents ofthe features shown and described o-r'portionsithereof, but recognize'that various modifications arerpossible within the scope of the invention ciaimecl;

I claim:

1. In a: telemeteringi system,. a plurality of:

transmitters, oneuforserrding cuclicalirnpulses of durations corresponding to valuesoi avariable determined; hiigher range, a'telemetric receiver.

to which saidstransmittersare adapted torbe connected in parallel, and means controlled by values;

of saidavariable-forselectively connecting said transmittersto saidlreceiver.

2. In alrtelemetering system, a plurality of i transmitters; one for-sendingcyclical impulses oi? durations :corresnondhrghto values of a variable within a'predete-rmined low range end'the other for sending :cyclical impulses of durations corresponding tovaluesoftsaid variable within a predetermined high'er range, a telemetric'recelverto which saddrtransmitters are adapted to be connected in parallel, andmeans controlled by said receiver "tori connecting one of said transmitters to said receiver wheny said values are in said low range and Torconnecting the other of said transmittersr toosaidzreceiver: when "said values are in electrical: impulse of a duration correspondingtoza otzsaidwariablewithm said low range,

a second transmitter having an element movable in response to values of said variable magnitude extending into a range substantially higher than the first-mentioned range and a rotatable cam cooperating with said element for sending in a cycle of rotation of said cam an impulse of a duration corresponding to a value of said variable outside said lower range, and means for rendering the first transmitter eifective and the second ineffective when the values of said variable ma nitude are in said lower range.

4. Telemetric apparatus comprising a transmitter having an element movable in response to low range values of a variable magnitude and a rotatable cam cooperating with said element for sending in a cycle of rotation of said cam an electrical impulse of a duration corresponding to a value of said variable within said low range, a second transmitter having an element movable in response to values of said variable magnitude extending into a range substantially higher than the first-mentioned range and a rotatable cam cooperating with said element for sending in a cycle of rotation of said cam an impulse of a duration corresponding to a value of said variable outside said lower range, and means for rendering the first transmitter effective and the second ineffective when the values of said variable magnitude are in said lower range, and for rendering the second transmitter efiective and the first ineffective in response to a predetermined maximum value of said lower range.

5. Telemetric apparatus comprising a transmitter having an element movable in response to low range values of a variable magnitude and a rotatable cam cooperating with said element for sending in a cycle of rotation of said cam an electrical impulse of a duration corresponding to a value of said variable within said low range, a second transmitter having an element movable in response to values of said variable magnitude extending into a range substantially higher than the first-mentioned range and a rotatable cam cooperating with said element for sending in a cycle of rotation of said cam an impulse of a duration corresponding to a value of said variable outside said lower range, a receiver to which said transmitters are adapted to be connected in parallel, said receiver having an element positionable in accordance with values of said variable magnitude, and switching means controlled by said receiver element for maintaining the first transmitter connected to said receiver when said values are within said range and for disconnecting said first transmitter from said receiver and connecting the second transmitter thereto in response to a predetermined maximum value from said first transmitter.

6. Telemetric apparatus comprising a receiver having an element movable to different positions in response to signals corresponding to values of a variable magnitude, means for connecting said receiver to either of a plurality of telemetric transmitters, and switching means controlled by said element for maintaining said receiver connected to one of said transmitters when said values in a predetermined low range and for connecting the other of :aid transmitters to said receiver for values exceeding said range.

'2. Telemetric apparatus comprising a receiver having an element movable to different positions throughout a given range in response to signals corresponding to values of a variable magnitude, means for connecting said receiver to either of a plurality of telemetric transmitters, and switching means operable by said element for maintaining said receiver connected to one of said transmitters when said values are in a predetermined low range and for disconnecting said receiver from the last mentioned transmitter and connecting the receiver to the other of said transmitters upon arrival of said element at a given position in its range of movements.

FRANCIS H. CARY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,102,234 Bliss July 7, 1914 2,333,083 Dueringer Nov. 2, 1942 2,443,351 Green June 15, 1948 2,533,091 Campani Dec. 5, 1950 2,536,465 Reeves Jan. 2, 1951 

